Updated for 2011, the Mercedes CL550 is a personal luxury coupe with generous dimensions, plentiful power, a great presence on the road, and substantial mass. In years past, this recipe has yielded superb comfort and satisfying performance. Not to mention envious glances from fellow motorists.

There were many plaudits, but fuel economy wasn’t one of them. The car’s gas-guzzler tax—$1300 during the 2010 model year—was simply accepted as part of the base price. That undesirable element of the car’s persona came to an end late Tuesday when Mercedes-Benz North America received word from the EPA labs that the 2011 CL550 was rated for 15 mpg city and 23 highway, up from 14/21. Guzzler tax: zero.

It’s a remarkable achievement for a car that tipped the Car and Driver scales at a hefty 4699 pounds. It’s even more remarkable for a car that brings increased power to the game—429 hp and 515 lb-ft of torque from a 4.7-liter twin-turbo V-8. The new engine makes use of a clutched alternator to eliminate the accessory’s drag, only engaging while the car is coasting, and therefore increasing fuel economy.